This invention relates to urethane polymer compositions, particularly moisture-reactive hot-melt urethane polymer compositions useful as adhesives and to a method for bonding substrates with such compositions.
The use of castor oil as a component in urethane polymer compositions is known in the art, as described in Polyurethane Handbook, 2nd edition, edited by G. Oertel, Hanser Publishers, 1993. Castor oil is thought to provide crosslinking to the composition. U.S. patent application Ser. No. 09/843706 discloses moisture-reactive hot-melt adhesives that incorporate castor oil into a polyurethane prepolymer-forming reaction mixture containing polyol and polyisocyanate. These adhesives achieve good properties, but alternatives to castor oil are desired in order to adjust the formulation to achieve specific balance of properties.
UK Patent 2278350 discloses the use of a hydroxylated diglyceride or triglyceride of one or more long-chain ethylenically unsaturated fatty acids as the sole polyol in a cured urethane polymer composition. U.S. Pat. No. 4,742,112 discloses a polyol mixture having polyhydroxyl ricinoleate compound and C2–C6 hydrocarbon polymer having at least one hydroxyl group.
The problem faced by the inventor is the provision of alternatives to unmodified castor oil as one of plural polyols in a moisture-reactive hot-melt adhesive composition. In addition, it is desirable to find useful polyols other than unmodified castor oil that are derived from renewable and/or natural sources. Surprisingly, the inventor found that incorporation of various hydroxyl-functional fatty compounds other than unmodified castor oil in urethane compositions yielded moisture-reactive adhesives with useful properties.